Without Anthony, the Knicks fell to the Rockets 91-86.
Anthony appeared to land awkwardly after attempting a jump shot with two minutes to play in the second quarter.
He tried to play through the injury but asked to be taken out of the game on the next possession.
After the game, Anthony went to a doctor in Houston to receive pain medication for the spasms that was not available at the arena, a team official said.
Anthony flew with the Knicks to Dallas for Wednesday night's game against the Mavericks but is listed as doubtful to play.
Teammate J.R. Smith said Anthony was in significant pain Monday night.
"He could barely talk, he said very few words," Smith said. "You could tell the pain he was in."
Head coach Derek Fisher was unsure of the condition of Anthony's back on Tuesday but said the Knicks would be patient with their star.
"As far as I'm aware, back spasms isn't really something that you can push or rush," Fisher said. "Until you can actually play without being in spasm, there isn't anything you can really do. Hopefully that will be soon. His back will be the only indicator of how soon that can be. I don't think there's anything we can necessarily do to rush that right now."
This is the second injury for Anthony thus far this season. He revealed last week that he is playing with discomfort in his left knee that first surfaced during the second game of the season.
Anthony is leading the Knicks in scoring with 23.9 points per game. Their next-highest scorer is Amar'e Stoudemire (12 points per game).
New York fell to 4-11 with Monday's loss and has dropped 10 of its past 12 games.